1. Field of the Invention
This invention relates generally to glazing-and-frame construction and more particularly to fenestration sealed frame, insulating glazing panels.
2. Description of the Prior Art
A conventional window consists of an insulating glass unit supported within a separate frame. Traditionally, the frame was made from wood or metal profiles, but increasingly plastic profiles made from such materials as polyvinyl chloride (PVC) or pultruded fibreglass are being substituted.
A traditional insulating glass unit generally consists of two or more glass sheets that are typically separated by a hollow aluminum spacer bar that is filled with desiccant bead material. With a conventional dual-seal unit, thermoplastic polyisobutylene material is applied to the spacer sides, and the outward facing channel between the glazing sheets and the spacer is filled with structural thermosetting sealant.
Because of the high thermal conductivity of the aluminum spacer, various efforts have been made in recent years to manufacture the hollow spacer from rigid low conductive plastic material. U.S. Pat. No. 4,564,540 issued to Davies describes the substitution of a rigid hollow fibreglass pultrusion for the aluminum spacer. Although a substantial development effort was carried out, this product has not yet been successfully commercialized and the technical problems include moisture wicking at the corners, glass stress breakage, and poor argon gas retention.
One solution to the problem of glass stress breakage is to manufacture the spacer from flexible material. U.S. Pat. No. 4,831,799 issued to Glover et al describes a flexible rubber foam spacer that is desiccant-filled with pre-applied pressure sensitive adhesive on the spacer sides. This flexible foam spacer has been commercialized under the name of Super Spacer®. In addition to featuring a low conductive spacer, another innovative feature of a Super Spacer® edge seal is that the traditional roles of the two perimeter seals are reversed. The inner PSA seal is the structural seal, while the outer seal is the moisture/gas barrier seal that is typically produced using hot melt butyl sealant.
In the past ten years, other warm-edge technologies have been developed where the traditional aluminum spacer has been replaced by a spacer made from a more insulating material, and these other warm-edge technologies include PPG's Intercept® and AFG's Comfort Seal® product. In total, these thermally improved warm-edge technologies have now gained about an 80 per cent share of the North American market.
In addition to reducing perimeter heat loss, these new warm edge products can also improve the efficiency and the speed of manufacturing the insulating glass units. These system improvements include manufacturing the edge seal as a metal re-enforced butyl strip (Tremco's Swiggle Seal®); roll forming the metal spacer and incorporating a butyl desiccant matrix and an outer butyl sealant (PPG's Intercept®); and manufacturing the spacer from EPDM foam with pre-applied butyl sealant and a desiccant matrix (AFG's Comfort Seal®). Although these improvements allow for the automated production of insulating glass units, residential sash windows still tend to be manufactured using largely manual assembly methods and typically, window frame fabrication is more labor intensive than sealed unit production.
One way of improving window assembly productivity is to fully integrate the frame and sealed unit assembly. In the presentation notes for the talk entitled Extreme Performance Warm-Edge Technology and Integrated IG/Window Production Systems given at InterGlass Metal '97, Glover describes a PVC sealed frame window system developed by Meeth Fenester in Germany. With this system, there is one continuous IG/window production line and using an automated four point welder, a PVC window frame is assembled around a double glazed unit. As noted in the paper, some of the concerns with the Meeth system include a problem of broken glass replacement, recycling/disposal of PVC window frames, and the technical risks of no drainage holes.
For window energy efficiency, most of the recent focus has been on improving the thermal performance of insulating glass units. Increasingly, it is being realized that substantial additional improvements will only be feasible through the development of new window frame types and technology. In a technical paper entitled Second Generation Super Windows and Total Solar Home Powered Heating, and presented at the Window Innovations '95 world conference in Toronto, Canada, Glover describes a second generation Super Window consisting of an exterior high performance triple glazed window and an interior high performance double glazed panel. By using motorized hardware, both the exterior and interior windows overlap the wall opening and this allows for a significant increase in solar gains and overall energy efficiency. However although significant energy efficiency improvements are achieved, the installation of the conventional casement window is very complex and this is primarily due to the extended width of the conventional window frame.